PHYSICS

 Question: What are subjective and objective properties of sound ? Answer : Subjective properties are basically the properties which can be measured directly. Loudness, pitch (shrillness) and quality(Timbre) of sound are subjective properties. But these properties  are related to the the measurable quantities  called objective properties.  Objective properties are the properties which can be measured. Intensity,  Amplitude, frequency, wavelength,  time period, intensity, fundamental frequency,  subsidiary frequencies are objective properties.  Loudness depends on amplitude,  intensity of the sound. Pitch(shrillness) depends on frequency. Quality (Timbre) depends on waveform( combination of primary and subsidiary notes).

 QUESTION: Why is loud sound heard at RESONANCE?  ANSWER: Loud sound is heard at RESONANCE because  amplitude increases when external  frequency is equal or integral multiple of the natural frequency of vibrating body.

Water has high specific heat capacity 4200J/(Kg°C) so it can absorb large amount of heat without much rise in it's own temperature.

 Islands or coastal areas enjoy moderate climate. Why? Ans. Water has higher heat specific capacity than the land due to which there is the continuous formation of sea breeze and land breeze near the coastal areas. This keeps the temperature moderate.

If no heat is exchanged with surrounding, heat lost by the hot body is equal to heat gained by the cold body. 

Plants and animals have 70-80% water so that they can maintain body temperature as water has high specific heat capacity.

Farmers fill their crop fields with water to protect from frost: why? Water has high specific heat capacity so it delays the surrounding temperature to fall to zero degree Celsius ,thus protecting the crops from frost

Why is water used in fomentation ? Water has high specific capacity due to which it cools slowly and imparts large amount of heat to our body.

ICSE and ISC semester 1 exams to be held in November 2021 is postponed. New datesheet will be released later.  It is now assumed that exam will be in offline mode.

PHYSICS REVISION TEST CLASS 10 , MACHINESS AND REFRACTION OF LIGHT ATTEMPT ALL QUESTIONS.  Q1. Give two reasons for a  single movable pulley not to be 100% efficient. 2 Q2. What is the purpose of a Jack in lifting a car by it ? 2 Q3. Stars twinkle in the sky . Give reason.  2 Q4. Draw a labelled diagram of a block and tackle system with velocity ratio 5.     2 Q5 Name the single pulley with mechanical advantage more than one. State  its one disadvantage.2 Q6. State two laws of refraction 2 Q7 State two factors affecting refractive index of a medium. State the effect also.2 Q8. Which colour out of green and orange , is deviated the most. Give reason for your answer. 2 Q9. A water pond appears 1.35 m deep. If the refractive index of water is 4/3, find the actual depth of the pond. 2 Q10. What is total INTERNAL reflection?  2 Q11.Draw a diagram for the deviation of a light ray by 90°. 2 Q12 Which colour of the visible light has maximum critical angle...

 CLASS 9 Physics   Q1 Name any two basic quantities and write their SI units.  Q2.Name any two derived quantities and write their SI units. Q3 What are the three requirements for selecting a unit of a physical quantity.?  Q4. Define “light year".  Q5. Compare the time periods of two pendulum of length 4m and 25 m.   Q6. State two factors affecting the time period of a pendulum. State the effects also.    Q7. Distinguish between speed and velocity.  Q8. A car is moving with a velocity of 20 m/s. The brakes are applied to retard it at a rate of 2m/s². What will be the speed after 5 s of applying the brakes?   Q9. What does the slope of following graphs represent?  i) displacement-time  graph  ii) velocity-time graph    Q10. Derive the relation: S=ut + ½at² ( any method).  Q11. A body moves from rest with a uniform acceleration and travels 270 m in 3 s. Find the velocity of the  bo...

There are two types of charges because we can establish charges only by loss or gain of electrons present in the orbits of an atom.  By losing electrons  a body gets positively charged and by gaining electrons it gets negatively charged.  Electron is the fundamental charge. It's taken as negatively charged. 

 Q. Why do you need moisturising cream in winter season? Answer: As the humidity is low in winter season where there is no winter rainfall, skin loses water due to evaporation and has tendency to dry quickly. To prevent this we need moisturising cream.